Basic Java Help

[Rainigul]

Free cookies for anyone who can tell me the answer to this.

On paper, write a method called sum with a while loop that adds up all numbers between two numbers a and b, inclusive, and returns the sum as its result. The values for a and b can be passed to the sum method as parameters. For instance: sum(1, 5) would return the value 15 (i.e., 1 + 2 + 3 + 4 + 5).

[EvGa]

Have you attempted to write the method on your own? Is this for a class?

What have you got so far?

Hint: Have your while loop compare a to b. You'll need to increment a.

[Azilius]

Doing my first Java lab tomorrow..maybe I'll post an answer after that. Google some sample code to help yourself out, this question shouldn't take long.

[Rainigul]

This is for a class, and nothing I've tried so far has worked. I'm either getting "void" type not allowed here, or other stupid errors. I'm about to throw this PC against the wall. Evga do you actually know what is the answer, would appreciate seeing it so I can figure out what I'm doing wrong.

[cpinney]

post what code you do have, would make it easier to diagnose the problem.

[EvGa]

Yes, I do know the solution, but for you to learn it is best to post what you have then try from there.

To get rid of any problems, format your class/main as follows. This will compile and run fine, just fill in the method:

Code: Select all

public class problem {

    public problem() {
    }

************************************************************
    public static int sum(int a, int b){
       
       //while loop goes here
       
    }
************************************************************

    public static void main(String[] args) {
        
        System.out.println("Result from sum(): " + sum(1,5));

    }
}

EDIT: Well, it will compile and run fine once you give the method a return statement...

[NuclearSilo]

Too easy (for me). But post your code first, you'll learn from your mistake

[only_me]

i dunno java but for C++ is for(i=a;i<=b;i++) sum+=i;
lawlz

[NuclearSilo]

i dunno java but for C++ is for(i=a;i<=b;i++) sum+=i;
lawlz

do you ever read? it says using while loop

[only_me]

int sum(int a,int b)
{int x,y,s=0;
if(a<b) {x=a;y=b;}
else {x=b;y=a;}
while(x<=y)
{s+=x;x++;}
return s;}

[EvGa]

And now the OP has to do no work to figure it out on his own...

[Rainigul]

Sorry, didn't update this. Figured it out a few hours after I posted.

Code: Select all

public void sum(int a, int b)
{
int first = a 
int last = b
int total = 0

while (first<=last)
{
total = total + first;
first = first + 1
}
System.out.println(total);
}

[EvGa]

That works except it doesn't return the value like the question asks, it simply prints it out.

Here is the simplest way:

Code: Select all

public int sum(int a, int b){

        int result = 0;
      while(a <= b){
         result += a;
         a++;
      }
      return result;
}

Then run it in your main and print the result.

Code: Select all

public static void main(String[] args) {
        System.out.println(sum(1,5));
}

In your method, where you have "void", that signifies the return type of the method, void meaning it returns nothing. The question asks to return the answer so you need a return type of int and inside the method you have to "return" the final answer. This allows the method to be called by your program and the method to pass a result (answer, an int in this case) back to the calling program (main method).

[only_me]

That works except it doesn't return the value like the question asks, it simply prints it out.

Here is the simplest way:

Code: Select all

public int sum(int a, int b){

        int result = 0;
      [b]while(a <= b)[/b]{
         result += a;
         a++;
      }
      return result;
}

Then run it in your main and print the result.

Code: Select all

public static void main(String[] args) {
        System.out.println(sum(1,5));
}

In your method, where you have "void", that signifies the return type of the method, void meaning it returns nothing. The question asks to return the answer so you need a return type of int and inside the method you have to "return" the final answer. This allows the method to be called by your program and the method to pass a result (answer, an int in this case) back to the calling program (main method).

what do u do if u have a =10 and b = -3

[EvGa]

what do u do if u have a =10 and b = -3

You really think his assignment is concerned with checking input constraints? This question was beyond simple, I'm going out on a limb here, but I bet this is an intro class and they are no where near concerned with checking things like that.

If he feels that the class is at that level, then by all means, add the few lines to check a and b. I don't think it is.